1# Input Device Development 2 3## When to Use 4 5Input device management provides functions such as listening for device hot swap events and querying the keyboard type of a specified device. For example, as a user enters text, the input method determines whether to launch the virtual keyboard based on whether a physical keyboard is currently inserted. Your application can determine whether a physical keyboard is inserted by listening to device hot swap events. 6 7## Modules to Import 8 9```js 10import inputDevice from '@ohos.multimodalInput.inputDevice'; 11``` 12 13## Available APIs 14 15The following table lists the common APIs for input device management. For details about the APIs, see [ohos.multimodalInput.inputDevice](../reference/apis/js-apis-inputdevice.md). 16 17| Instance| API | Description| 18| ----------- | ------------------------------------------------------------ | -------------------------- | 19| inputDevice | function getDeviceList(): Promise\<Array\<number>>; | Obtains the list of input devices.| 20| inputDevice | function getKeyboardType(deviceId: number): Promise\<KeyboardType>; | Obtains the keyboard type of the input device.| 21| inputDevice | function on(type: "change", listener: Callback\<DeviceListener>): void; | Enables listening for device hot swap events.| 22| inputDevice | function off(type: "change", listener?: Callback\<DeviceListener>): void; | Disables listening for device hot swap events.| 23 24## Virtual Keyboard Detection 25 26When a user enters text, the input method determines whether to launch the virtual keyboard based on whether a physical keyboard is currently inserted. Your application can determine whether a physical keyboard is inserted by listening to device hot swap events. 27 28## How to Develop 29 301. Call the **getDeviceList** API to obtain the list of connected input devices. Call the **getKeyboardType** API to traverse all connected devices to check whether a physical keyboard exists. If a physical keyboard exists, mark the physical keyboard as connected. This step ensures that your application detects all inserted input devices before listening for device hot swap events. 312. Call the **on** API to listen for device hot swap events. If a physical keyboard is inserted, mark the physical keyboard as connected. If a physical keyboard is removed, mark the physical keyboard as disconnected. 323. When a user enters text, check whether a physical keyboard is connected. If a physical keyboard is not connected, launch the virtual keyboard. 33 34 35```js 36import inputDevice from '@ohos.multimodalInput.inputDevice'; 37 38let isPhysicalKeyboardExist = true; 39try { 40 // 1. Obtain the list of input devices and check whether a physical keyboard is connected. 41 inputDevice.getDeviceList().then(data => { 42 for (let i = 0; i < data.length; ++i) { 43 inputDevice.getKeyboardType(data[i]).then(type => { 44 if (type === inputDevice.KeyboardType.ALPHABETIC_KEYBOARD) { 45 // The physical keyboard is connected. 46 isPhysicalKeyboardExist = true; 47 } 48 }); 49 } 50 }); 51 // 2. Listen for device hot swap events. 52 inputDevice.on("change", (data) => { 53 console.log(`Device event info: ${JSON.stringify(data)}`); 54 inputDevice.getKeyboardType(data.deviceId).then((type) => { 55 console.log("The keyboard type is: " + type); 56 if (type === inputDevice.KeyboardType.ALPHABETIC_KEYBOARD && data.type == 'add') { 57 // The physical keyboard is inserted. 58 isPhysicalKeyboardExist = true; 59 } else if (type == inputDevice.KeyboardType.ALPHABETIC_KEYBOARD && data.type == 'remove') { 60 // The physical keyboard is removed. 61 isPhysicalKeyboardExist = false; 62 } 63 }); 64 }); 65} catch (error) { 66 console.log(`Execute failed, error: ${JSON.stringify(error, [`code`, `message`])}`); 67} 68 // 3. Determine whether to launch the virtual keyboard based on the value of isPhysicalKeyboardExist. 69 // TODO 70``` 71